(CNN) -- World No. 2 Rafael Nadal is still on course for his first Miami Masters title after beating the Czech Republic's Radek Stepanek 6-2 6-2 in the third round of the U.S. hard-court tournament.
Spain's 10-time grand slam winner has been runner-up at the event on three occasions, including last year when he lost to Novak Djokovic, who went on to dethrone him at the top of the rankings.
Nadal took just 87 minutes to record a sixth consecutive win over 25th seed Stepanek on Sunday, setting up a clash with No. 16 Kei Nishikori -- who also beat Czech opposition in the shape of Lukas Rosol.
"He's a fantastic player and it will be a very difficult match for me," Nadal said of Japan's 22-year-old rising star.
"He has a big talent to hit the ball very early, to play very aggressive. So he will be a really tough opponent."
World No. 4 Andy Murray reached the last 16 without hitting a ball, after his in-form third-round opponent Milos Raonic was forced to pull out due to an ankle injury in Key Biscayne.
"The doctor doesn't think it's anything big. It probably just needs a couple days of rest and, with treatment, it should be OK in a week," said the Canadian, who has already won titles in Chennai and San Jose this year.
Murray will now face Gilles Simon for a place in the quarterfinals after the French 13th seed won 7-6 6-4 against Austrian 22nd seed Jurgen Melzer.
In other third-round matches, seventh-seeded Czech Tomas Berdych slumped to a shock 6-3 2-6 6-4 defeat by Grigor Dimitrov, who beat a top-10 player for the first time in his career.
The Bulgarian next faces Serbian ninth seed Janko Tipsarevic, who saw off Ukrainian No. 18 Alexandr Dolgopolov 6-4 5-7 6-2.
French sixth seed Jo-Wilfried Tsonga defeated No. 32 Philipp Kohlschreiber 6-4 7-6, and will next face another German -- No. 19 Florian Mayer. The winner of that match will face Nadal or Nishikori.
In the women's section, the unseeded Venus Williams, who was handed a wildcard to compete in Florida, is also through to the last 16.
The American, who was diagnosed with the incurable Sjogren's syndrome before the 2011 U.S. Open, was made to battle hard before defeating Canadian Aleksandra Wozniak 4-6 6-4 7-6.
She next faces fellow former world No. 1 Ana Ivanovic. The Serbian 15th seed overcame Slovakia's No. 20 Daniela Hantuchova 6-2 7-6 (7-2).
World No. 1 Victoria Azarenka, the defending champion, thrashed British wildcard Heather Watson 6-0 6-2.
The Australian Open champion will play No.16 Dominika Cibulkova after the Slovakian beat China's Zheng Jie.
Polish fifth seed Agnieszka Radwanska set up a clash with Spanish wildcard Garbine Muguruza Blanc, who shocked Italy's No. 24 Flavia Pennetta 6-2 1-6 7-6.
French seventh seed Marion Bartoli will face Russia's No. 22 Maria Kirilenko in the last 16 after both won comfortably.